From the S2 Github (official site for GN):
“GhostNet is the overarching term for a collection of communications networks set up to allow users around the world to exchange information without relying on pre-established infrastructure. Far from being just an emergency plan, GhostNet is intended to ease the transition of radio technology into everyday life. Though radio networks cannot truly replace the internet, we hope that we can replace a substantial portion of a person’s daily information requirements, and promote a culture of off-grid information sharing.”
In essence, GN is the radio version of the wire which is decentralized, that S2 Monitors each Thursday night and operates via the Ham radio frequency. Although to broadcast you must have a Ham radio license, anyone with JS8 Call can monitor with a WebSDR reciever.
S2 usually summarizes the activity on GhostNet that he observed on his weekend update videos.
Video explainer by s2: